RuII-p-cymene (Ru2-p-cymene) complexes of pyrazolylbenzimidazole ligands as potential anticancer agents

Chakraborty, Ayan (2022) RuII-p-cymene (Ru2-p-cymene) complexes of pyrazolylbenzimidazole ligands as potential anticancer agents. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Ayan Chakraborty (15RS039)) 15RS039.pdf - Submitted Version Restricted to Repository staff only Download (11MB)

Abstract

Cancer is a globally threatening disease, taking major toll on human life every year. Drugsor chemical agents that are used to prevent the growth of cancer cells through inhibition of cell division (mitosis) are generally termed as chemotherapeutic agents. Small organic molecules, with varying modes of action, have been in the forefront for a considerable amount of time, generally used for treatment and preventive purposes. The serendipitous invention of cisplatin in 1845 and its approval for cancer therapy by FDA in 1978 uncovered a new era in the field of metal-based anticancer therapeutics. The research work produced in this thesis is mainly focused on design and synthesis of RuII (p-cymene) complexesto investigate the effects of halide variation in ligand and change in coordinated halide on cytotoxicity and pathways of action. In Chapter I, contains introduction to cancers, hallmarks of cancer and types of organic-based chemotherapeutic agents. The discussion gradually moves on to the emergence of platinum-based drugs in clinic and clinical trials as well as to recent research. The discussion encompassed to metal (Ru, Ir, Pt) based kinase inhibitors and their impact on cancer. One important point is designing of ligand which is a key feature for successful kinase inhibitor. A comparative discussion on the dependence of inhibition activity on structural variation andalteration of coordinated halide is emphasized. The introduction chapter is ends with adiscussion on the scope of this thesis. In this chapter II, we have designed, synthesized & thoroughly characterized eight new organometallic Ru(II) complex having general molecular formula [RuII(η⁶pcymene)( L)X]⁺X⁻substituted at the 4 position of the pyrazole ring by Cl (II-L2), Br (II-L3), or I (II-L4) and X= Cl⁻ , I⁻]. Complexes II-1 and II-3 were also characterized by single-crystal X-ray crystallography. They crystallized as a monoclinic crystal system in space groups P21/n and P21/c, respectively. The complexes exhibit good solution stability at physiological pH 7.4. The iodido p-cymene complexes of pyrazolylbenzimidazole ligand (II-2, II-4, II-6 and II-8) are more resistant toward hydrolysis and less prone to aquation in comparison to their chlorido analogues (II-1, II-3, II-5, and II-7). Those complex (II-4 to II-8) show excellent cytotoxicity (IC50 ca. 9-12μM) against triple negative breast cancer cell (MDA-MB-231). The presence of halogen in ligand enhances the cytotoxicity, lipophilicity &cellular accumulation which show a good correlation with each other. The halido-substituted 2-(1H-pyrazol-1-yl)- 1H-benzo[d] imidazole ligands, designed as organic-directing molecules, inhibit vascular endothelial growth factor receptor 2 (VEGFR-2) phosphorylation. In addition, the ruthenium(II) complexes display a potential to bind to model DNA bases 9-EtG , which is confirmed by ¹H-NMR and ESI-HRMS. The complexes II-3 and II-7 demonstrated the capability of arresting the cell cycle in the G2/M phase and induce apoptosis. The inhibition of VEGFR-2 phosphorylation with the ligands II-L2 and II-L4 and the corresponding metal complexes II-3 and II-7 in vitro shows that the organic directing ligands and their complexes inhibit VEGFR-2 phosphorylation.Besides, II-L2, II-L4, II-3, and II-7 inhibit the phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and protooncogene tyrosine-protein kinase (Src), capable of acting downstream of VEGFR-2 and independently. Compounds II-L2, II-L4, II-3, and II-7 have a lesser effect on ERK1/2 and more prominently affect Src phosphorylation. The in vivo study of II-L2 and II-3 in the Tg(fli1:gfp) zebrafish model and shows that II-L2inmore effective in vivo compared to the complex II-3 in inhibiting angiogenesis. In Chapter III, we have synthesized and characterized six new organometallic Ru(II) complex (III-1 to III-6) having molecular formula [RuII(η⁶p-cymene)(L)X]X- where the ligand L is 2-(3,5-dimethyl-1H-pyrazol-1-yl)-1H-benzo[d]imidazole (III-L1) substituted at the 4 position of the pyrazole ring by Cl (III-L2), I (III-L4) and X= Cl⁻, I⁻]. The first ligand (III-L1) was synthesized by using a one pot method in POCl₃. Ligand III-L2&III-L3 were synthesized from III-L1 as a starting material using N-Chlorosuccinimide (for III-L2) & iodine/Ceric ammonium nitrate (for III-L3). The metalation was carried out using organometallic ruthenium dimer [Ru₂μ₂-X₂(η⁶p-cymene)₂X₄] where X=Cl, I. All metal complex (III-1 to III-6) was spectroscopically characterized using ¹H-NMR, proton decoupled ¹³C-NMR, HMQC, ESI-HRMS, elemental analysis, FT-IR, UV-Vis. Lipophilicity (log DO/W) study indicates that insertion of halogen on ligand makes the system more lipophilic whereas internalization experiment by ICP-MS in MDA-MB-231 (a triple negative breast cancer cell line) shows that presence of halogen actually helps the molecule to cross the cell membrane which constitute of phospholipid. In this chapter IV, we have synthesized and characterized six set of novel organometallic Ru(II) complex (IV-1 to IV-6) having molecular formula [RuII(η⁶pcymene)( L)X]X⁻ where the ligand L is 2-(3-methyl-1H-pyrazol-1-yl)-1H-benzo[d]imidazole (IV-L1) substituted at the 4 position of the pyrazole ring by Cl (IV-L2) and X= Cl⁻, Br⁻, I⁻]. The ligands (IV-L1 & IV-L2) were synthesized by using a one pot method in POCl₃ from a cyclic urea (IV-LI). The metalation was carried out using the organometallic ruthenium dimer [Ru₂μ₂-X₂(p-cymene)₂X₄] where X=Cl, Br, I. All metal complexes (IV-1 to IV-6) was spectroscopically characterized using ¹H-NMR, proton decoupled ¹³C-NMR, HMQC, ESIHRMS, elemental analysis, FT-IR, UV-Vis. Lipophilicity (log DO/W) study indicates that insertion of halogen on ligand makes the system more lipophilic as found in earlier chapters. The lipophilicity is in good correlation with internalization experiment by ICP-OES in MDAMB- 231 (a triple negative breast cancer cell line). The ICP-OES result shows that the presence of halogen actually helps the molecule to cross the cell membrane which constitute of phospholipid. It is also evident that halido (Cl, Br, I) leaving group has very little effect on lipophilicity & cellular internalization suggesting that in most of the complexes of halide may dissociatedwith time& exchanged with chloride in solution converting them into chlorido complexes eventually. In chapter V, Ru(II) complex (V-1 to V-3) having molecular formula [RuII(η⁶-pcymen)( L)Cl]Cl where the ligand L is 2-(3-methyl-1H-pyrazol-1-yl)-1H-benzo[d]imida N- ((1H-benzo[d]imidazol-2-yl)methyl)-2,6-dimethylanilinezole(V-L1),N-((1Hbenzo[ d]imidazol-2-yl)methyl)-2,6-diisopropylaniline (V-L2) & N-((1H-benzo[d]imidazol-2- yl)methyl)-N-methylaniline (V-L3). The ligands (V-1 to V-3) were synthesized by reacting 2-(bromomethyl)-1H-benzo[d]imidazole (2-BrCH₂Pyz) and respective anilines (2,6-dimethylaniline, 2,6-diisopropylaniline, N-methylaniline) in presence of base which follows a typical nucleophilic substitution (SN). The 2-BrCH₂Pyz isobtained from o-phenylenediamine & bromoacetic acid through an acid catalyzed cyclization reaction. All ligands (V-L1 to VL3) & metal complexes (V-1 to V-6) was spectroscopically characterized using ¹H-NMR, proton decoupled ¹³C-NMR, HMQC, ESI-HRMS, elemental analysis, FT-IR, UV-Vis spectroscopy. Complex V-1 was crystallized in triclinic crystal system with P-1 space group. Chapter VI discusses on the syntheses of three different type of structurally diverse ligands inspired by previously reported structures. The first kind of ligand is pyrazolyltriazine (VI-L1, VI-L2), whereas the other two types are pyrazolyl pyridine (VI-L3) &diphenylethane-1,2-diimine (VI-L4 & VI-L5). The two C—Cl bond in dichloropyrazine system was effectively hydrolyzed into C=O bond during the synthesis of the two complex VI-1 & VI-2. In this case RuII metal precursor also acts as a Lewis acid as. The formation of C=O bond was further confirmed by single crystal XRD (VI-1) and ESI-MS. Complex VI- 3&VI-4 arechlorido and iodidocomplexes of 4-chloro pyrazolyl pyridine. The rest of the two complexes (VI-5, VI-6) are Pt(II) complex of diimine ligand containing morpholine. The Pt(II) dichloro complex was characterized by ¹H-NMR, ESI-HRMS & CHN. The change in chemical shift is quite remarkable (~0.7 ppm), which suggests the formation of Pt(II) complex. The presence of sterically hindered group (Me, i-Pr) may influence its reactivity and solution behavior. All the complexes (VI-1 to VI-6) may show a good biological and physicochemical activity.

Actions (login required)

View Item